So, I have always been salting the water first when cooking pasta. Another amateur cook friend insists on salt after boil because it raises boil temperature elsewise. I keep telling him I don't care since it only raises it about one Fahrenheit for an ounce (damn imperial system...) so not a big deal. Just now I heard Gordon Ramsay say "What's the number one rule when cooking pasta? Salt in first" to his son and I wanna know if I can substantiate my claim to salt in first. Does anyone have a clue why he might have said this? Is there some chemistry going on there that can help? Edit: Not why but when. Stop flagging duplicate please.
From a chemistry perspective there's no difference between the approaches, either way you're ending up with the same amount of water and salt with the same boiling point.
Ramsey is saying salt in first because he's adding the salt to the water before the pasta, not before heating the water. It makes sense to add the salt to the water before heating it because:
- It's one less thing to do later: by the time you're ready to add the pasta to the water you might be busy, adding the salt to the water first saves you the step later
- You're less likely to forget to add it: again, if you're busy later you might skip the step
Actually really does not matter. Yes, salted water boils at 101°C, but it does not matter if you put in in first (say 20°C) and heat it up to 101°C or if you are adding it to the boiling water (100°C) and need to bring it up to 101°C to keep it boiling.
There's only one reason that I can think of where it matters -- when cooking in stainless steel.
As I understand it, the problem is when you have both oxygen and dissolved salt in the water, as there will be a chemical reaction that will pit the metal. If you heat the water first, it can't hold oxygen (which is why factories pumping hot water into streams causes fish kills), and you won't have the problems.
So, for stainless -- heat first, then salt.
(This came up a few years back, when it was revealed that Olive Garden didn't salt their pasta so they could get a longer warranty on their pots)
Salting your water before you heat it appears to be an old wives tale.
From what I have read, using a stainless steel pot can result in some pitting over time. This is basically a form of rust, caused by the chloride in salt, oxygen in water, and chromium in stainless steel. Salting your pot after the water boils is better for these pans.
When your pan is very clean, and you add the salt around boiling point, it may be that your water is overheated somewhat and you get some explosive bubling. The bubbles will subside quickly to regular boiling.
I used to do this sometimes with a stainless steel pan for my own amusement, but its safer not to and add the salt earlier.